I just found the problem. Hadn't flown the 737 in well over a year and had a different joystick / throttle when I did. When I calibrated the Saitek throttle quadrant which I got about 6 months ago, somehow it was sent to FSUIPC calibration for the 737 instead of just straight to the sim. I just parked the 737 after a flight, and noticed with the engines still running that when I pulled the throttle to the low stop, before the reverse switch, that the reversers came on. I heard this from the cockpit, and went outside to look, and sure enough the reverser was engaged. I set the setting for the Throttle in FSUIPC to direct instead of calibrating, and problem is instantly fixed.

MCP speed. Right now I am flying an approach at 220 knots, and if I pull throttle to minimum, the power immediately drops to flight idle and it starts slowing down. Move the throttle just a tad away from the bottom, and the power comes back up , and speed returns .